Polarization preserving projection screen with engineered pigment and method for making same

ABSTRACT

Polarization preserving projection screens provide optimum polarization preservation for 3D viewing. The projection screens additionally provide improved light control for enhanced brightness, uniformity, and contrast for both 2D and 3D systems. Generally, the disclosed method for providing a projection screen comprises stripping an optically functional material from a carrier substrate, thus creating engineered particles from the optically functional material. The engineered particles may then be deposited on a second substrate to create a substantially homogeneous optical appearance of the projection screen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/289,343, filed Dec. 22, 2009, entitled “Polarizationpreserving projection screen with engineered pigment,” the entirety ofwhich is herein incorporated by reference. This application is filedconcurrently with U.S. patent application Ser. No. 12/976,986, entitled“Polarization preserving projection screen with engineered particle andmethod for making same,” which claims priority to U.S. Prov. Pat. App.Ser. No. 61/289,346, filed Dec. 22, 2009, entitled “Polarizationpreserving projection screen with engineered particle,” the entirety ofwhich is herein incorporated by reference.

TECHNICAL FIELD

The present disclosure generally relates to front projection screens,and more specifically, to polarization preserving front projectionscreens.

BACKGROUND

Modern 3-dimensional (“3D”) cinema systems increasingly rely onpolarization as a means of delivering stereoscopic imagery to anaudience. Most of these systems place polarization control elements atboth the digital projector and the viewer, which in practice makes thescreen a contrast and/or cross-talk determining component. Manufacturersof front projection screens generally attempt to strike a compromisebetween image brightness uniformity and Polarization Contrast Ratio(“PCR”). Relative lack of efficiency of current screens (which has beendescribed as Total Integrated Scatter or “TIS”), along with inherentlight loss of most 3D delivery systems, further call for high peak gainto meet standards for image brightness. Conventional “silver-screens,”however, have performance deficiencies that are the result of severalstatistical variables, which make it virtually impossible to optimizePCR, gain profile and efficiency.

BRIEF SUMMARY

According to the present disclosure, a web shuffling method forproviding a projection screen may include stripping an opticallyfunctional material from a carrier substrate. The stripping may breakthe optically functional material into individual engineered particles.A coating may be distributed onto a second substrate to achieve asubstantially homogeneous optical appearance of the projection screen,and the coating may include the individual engineered particles.Additionally, a base diffuser material may be fabricated and the basediffuser material may be adjacent to the optically functional material.The fabrication of the base diffuser material further comprises holdinga predetermined tolerance, further wherein the predetermined toleranceis based on at least a difference between long-range statistics andensemble statistics. The distributed coating may provide a surface thatsubstantially approximates that of the base diffuser material.

Disclosed in the present application is a projection screen with asubstantially homogeneous appearance, in which the substantiallyhomogeneous appearance may be achieved through web shuffling. Theprojection screen may include a substrate and a coating adjacent to thesubstrate. The coating may be comprised of at least engineered particleswhich may be created by stripping an optically functional material froma carrier substrate. The engineered particles may be operable toprimarily determine the scattering behavior of light. Furthermore, themorphology of the engineered particles may be operable to primarily,statistically determine the macroscopic scatter behavior of theprojection screen. In one embodiment of the projection screen, thecarrier substrate may be a sacrificial carrier substrate.

According to another aspect, the present application discloses a methodfor providing a projection screen. The method may include stripping anoptically functional material from a first carrier substrate, creatingengineered particles from the optically functional material anddepositing the engineered particles on a second substrate to create asubstantially homogeneous optical appearance of the projection screen.The method may also include utilizing a diffuser to provide theoptically functional material, wherein the diffuser may be adjacent tothe first carrier substrate. Additionally, a first optical coating maybe deposited adjacent to the diffuser.

These and other advantages and features of the present invention willbecome apparent to those of ordinary skill in the art upon reading thisdisclosure in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example in the accompanyingfigures, in which like reference numbers indicate similar parts, and inwhich:

FIG. 1 is a schematic diagram illustrating the cross section of aconventional silver screen structure;

FIG. 2 is a schematic diagram illustrating a cross section of oneembodiment of a structure for a projection screen, in accordance withthe present disclosure;

FIG. 3 is a schematic diagram illustrating a perspective view of oneembodiment of a process for providing flake particles, in accordancewith the present disclosure;

FIG. 4 is a schematic diagram illustrating a spectrum of feature sizesand the ranges associated with particular screen characteristics, inaccordance with the present disclosure;

FIGS. 5A and 5B are schematic diagrams respectively illustrating oneembodiment of a defect before and after web shuffling, in accordancewith the present disclosure; and

FIG. 6 is a flowchart illustrating operations of one embodiment of amethod for providing a projection screen, in accordance with the presentdisclosure.

DETAILED DESCRIPTION

Generally, one embodiment of the present disclosure may take the form ofa method for providing a projection screen using web shuffling. In thisembodiment, the method may be achieved by stripping the opticallyfunctional material from a diffuser carrier substrate, creatingparticles of a size appropriate for the selected coating technology, andre-coating the particles on a screen substrate. In one exemplaryembodiment, the particles may be diffuser particles and may besubstituted for ball-milled aluminum typically used in a conventionalspray painting process. In another exemplary embodiment, a virtuallydeterministic engineered particle with prescribed scatter statistics mayrely primarily on web shuffling for the randomization needed to create asubstantially macroscopic homogeneous appearance.

Another embodiment of the present disclosure may take the form of aprojection screen. The projection screen may exhibit macroscopic scatterbehavior primarily determined by the statistics associated with themorphology of individual particles that may be coated on the projectionscreen substrate. Using embossing technology (e.g. UV embossing), theparticle slope probability statistics can be somewhat controlled, andmay provide statistically self-contained units that have somewhatpredictable scatter profiles, PCR and efficiency. This may lead tocoating processes that may be substantially predictable in particleslope probability statistics. By greatly reducing the influence of therandom processes discussed herein, surfaces may be made that decouplescatter profile shape/width from PCR.

Yet another embodiment of the present disclosure may take the form of aprojection screen with a substantially homogeneous appearance which maybe achieved via web shuffling. The projection screen may include asubstrate which may be coated with an optically functional material thatincludes engineered particles. The engineered particles may be createdby stripping a coating from a carrier substrate which may cause thecoating to break into individual engineered particles, and thendepositing the engineered particles on a projection screen surface tocreate a substantially homogeneous optical appearance of the projectionscreen.

It should be noted that embodiments of the present disclosure may beused in a variety of optical systems and projection systems. Theembodiment may include or work with a variety of projectors, projectionsystems, optical components, computer systems, processors,self-contained projector systems, visual and/or audiovisual systems andelectrical and/or optical devices. Aspects of the present disclosure maybe used with practically any apparatus related to optical and electricaldevices, optical systems, presentation systems or any apparatus that maycontain any type of optical system. Accordingly, embodiments of thepresent disclosure may be employed in optical systems, devices used invisual and/or optical presentations, visual peripherals and so on and ina number of computing environments including the Internet, intranets,local area networks, wide area networks and so on.

Before proceeding to the disclosed embodiments in detail, it should beunderstood that the invention is not limited in its application orcreation to the details of the particular arrangements shown, becausethe invention is capable of other embodiments. Moreover, aspects of theinvention may be set forth in different combinations and arrangements todefine inventions unique in their own right. Also, the terminology usedherein is for the purpose of description and not of limitation.

FIG. 1 is a schematic diagram illustrating the cross section of aconventional silver screen structure 100 used for stereoscopic 3Dimaging. The conventional silver screen 100 may include a substrate 110and a coating 120. Generally, conventional silver screen 100 may befabricated by spray-painting the coating 120 onto the substrate 110. Thecoating 120 may include resin 130, aluminum flake 140 and matting agents150. The flake 140 may be immersed in a transparent binder such as resin130. Additionally, the aluminum flake 140 may be ball-milled aluminumparticles or pigment. The matting agents 150 may be any type of particleto produce the desired optical characteristics and may be particles suchas silica.

Various optical characteristics, either qualitative or quantitative, maybe used to evaluate the optical performance of a projection screen suchas the conventional silver screen 100. The optical characteristics mayinclude measurements such as, but not limited to PCR, scatter profile,TIS, scattering from individual components of the projection screen,image brightness, image brightness uniformity, gain, gain profile and soon. The optical characteristics will be discussed in further detailbelow. The evaluation of conventional silver screens illustratesperformance deficiencies with one or more non-optimized, aforementionedoptical characteristics.

For example, conventional silver screens, generally, may demonstrate anon-axis circular PCR of 90:1 and may rarely exceed 120:1. The less thanoptimal on-axis circular PCR may be attributed to poor performance ofthe raw materials such as the substrate 110 and lack of process controlwhen fabricating one or more of the coating 120, the aluminum flake 140or resin 130. Additionally, the cross-talk term is characteristicallyangle neutral, so the PCR may also tend to degrade in proportion to thegain curve. The result may be screen performance that drives systemlevel PCR and thus may dictate the quality of the stereoscopic 3Dexperience. System level PCR may be composed of the combined effect ofmost or all of the components. Currently, the system level PCR may beprimarily determined by the screen PCR.

In FIG. 1, the individual components of the conventional silver screen100 may contribute to the optical characteristics. For example, thealuminum flake 140 may consist of statistically scattering edge andsub-micron features as well as planar (e.g., specularly reflecting)features that when combined with the statistics of particle stacking maydetermine the macroscopic scatter characteristics of the conventionalsilver screen 100. Although low-cost ball-milled aluminum particles maybeneficially broaden the scatter profile due to the relatively irregularshape/size of the aluminum particles, the aluminum particles may causeother issues from a polarization management perspective. When thepreviously-discussed issues are coupled with the statistics associatedwith the coating process, current screen manufacturing may lack thecontrol required to increase the diffusion angle without compromisingPCR. More specifically, as the probability of a highly sloped surfaceincreases, so too does the probability of a secondary reflection event,with the PCR suffering as a consequence.

One aspect of the present disclosure addresses the previously-discussedlimitations and may use a novel “web shuffling” technique in conjunctionwith roll-to-roll fabricated diffuser. Web shuffling is an averagingprocess, whereby engineered particles of a prescribed size may betransferred from a carrier substrate to a screen substrate using astatistical (or shuffling) process. According to the present disclosure,the shuffling process may be used to substantially homogenize one ormore non-uniformities that may occur in the manufacturing of the rawdiffuser stock. In one example, it may be understood thatnon-uniformities are substantially homogenized when the human eye cannotdetect the non-uniformities at one or more of the following scales: justresolvable dimension, just resolvable area, just noticeable difference,and so on. Each of the particle size and morphology, or both, may beoptimally selected such that each may provide a suitable approximationto the desired macroscopic scatter statistics. The particles may bemanufactured using roll-to-roll embossing technology, which produces theimproved optical quality reflective diffuser performance. The webshuffling of the present disclosure may allow for the elimination of theneed to manufacture roll-to-roll embossed diffuser on a wide-web that issubstantially defect-free and extremely uniform.

A technique involving web shuffling enables the substantialhomogenization of subtle non-uniformities that can result in the toolingfabrication, roll-to-roll manufacturing process, and vacuum opticalstack coating, without significantly sacrificing optical performance.The benefits of this approach for screen manufacturing can take manyforms, including: (1) Spatially averaging large scale variations indiffuser profile characteristics; (2) Azimuthally averaging the effectsof a directional diffuser (which can also vary spatially); (3)Randomization of diffraction artifacts resulting from periodicbase-material, and (4) Spatially averaging (or removing) gross defectmaterial, which can include one or more of drum seams, large facets,scuffs, and other macroscopic defects in the embossing and opticalcoating process.

A benchmark for stereoscopic 3D front projection screen performance isan engineered surface with a highly reflective (e.g., aluminum)conformal layer, as described in the commonly-owned U.S. PatentApplication Publication No. US 2009/0190210, which is herebyincorporated by reference. An engineered surface can be generateddirectly from a surface map file or a set of design rules, and thus canin principle provide a virtually ideal scatter profile, PCR, andefficiency. However, the fabrication of such a surface in sufficientsize to build a cinema screen can be challenging.

In one example, the fabrication of the previously-discussed surface mayinvolve fabricating and maintaining a roll-to-roll embossing tool thatmay have one or more of the following features: 1) no drum seams or nosubstantially significant drum seams; 2) no gross defects orsubstantially insignificant gross defects, either of which would avoidproducing repeating screen artifacts (e.g., voids that producemirror-like facets); and/or 3) a prescribed topography that isstatistically uniform over the entire tool. In order to avoid visuallyobjectionable diffraction artifacts and moire, a design may alsoincorporate feature randomization (versus a true periodic structure onthe roll-to-roll embossing tool). Moreover, the scatter statistics atthe web edges should be well matched, so that butt joinedstrips of filmdo not produce substantial visible intensity steps (when observing frommost or all locations in a theatre).

Given the scale and cost of the raw diffuser stock, acceptable yield maybe obtained if cosmetic defects resulting from the manufacturing andhandling of the material are virtually eliminated. Tighter statisticscan be obtained by using higher quality leafing pigments, which areoptically flatter and tend to align in the plane of the binder surface.However, surfaces made with optical quality flat metallic leafingpigments have inherently narrow scatter profiles (e.g., 5-15 degreehalf-power angle), producing screens with higher TIS, but poorbrightness uniformity as a function of viewing angle. Furthermore,techniques for broadening the scatter profile of optical quality pigmentby controlling the extent of leafing often lack manufacturingrobustness. Although a non-leafing pigment may be used, non-leafingpigment typically produces more of a bulk scatter, which is difficult tocontrol and is again at the expense of PCR. Importantly, web shufflingin conjunction with roll-to-roll fabricated diffuser may address thelimitations of both these technologies.

FIG. 2 is a schematic diagram illustrating a cross section of oneembodiment of a structure for a projection screen 200. The web-shuffledflake screen 200 may include a substrate 210 and a web-shuffled coating220. The web-shuffled coating 220 may include a fluid 230. The fluid 230may contain a transparent binder resin such as, but not limited to PVCresin, enamel, polyurethane, acrylic, lacquer, and the like, and/or someform of dilution, which can be either solvent aqueous-based. The fluid230 may serve as a carrier for the flake particles 240. The flakeparticles 240 may be engineered aluminum flakes or particles createdfrom at least one or more of a diffuser, a reflective coating andmultiple optical coatings. Additionally, the flake particles 240 mayoverlap one another on the substrate 210. In one embodiment, the flakeparticles may substantially cover most or all of the surface ofsubstrate 210. The fabrication of the web-shuffled flake screen 200 willbe described in detail below with reference to FIG. 3.

FIG. 3 is a schematic diagram illustrating a perspective view of oneembodiment of an apparatus 300 used in a process for providing the flakeparticles 240 described in FIG. 2. Apparatus 300 may include a substrate310, a diffuser 320, a release layer 330, optical coatings 340, and areflective layer 350. The diffuser 320 may be fabricated from an initialcontinuous surface (not depicted in FIG. 3). Additionally, the initialcontinuous surface and diffuser 320 of FIG. 3 may be measured andevaluated using similar functional specifications, each of which will bediscussed below. Furthermore, the fabrication of the initial continuoussurface will be discussed in further detail below.

The light scattering behavior of a surface fabricated according to thepresent disclosure is the result of several statistical processes.Generally, the compound statistics are the result of three manufacturingprocess steps; (1) Fabrication of the initial continuous surface, (2)Fabrication of discrete surface elements, and, (3) Deposition ofdiscrete surface elements. The following describes the fabricationprocesses and the parameters influencing first-order statistics, as wellas embodiments that most closely approximate the behavior of the idealsurface.

Fabrication of Initial Continuous Surface

The initial continuous surface may be fabricated using a number ofmanufacturing processes that substantially produce a predeterminedtopography. The preferred topography may be optically smooth, withslopes that vary spatially on a scale that is large relative to awavelength of illuminating radiation. In one embodiment, the initialsurface may be mastered using an analog photo-resist process, from whichmanufacturing tooling may be generated. The fabrication of themanufacturing tool may also include intermediate tooling steps inaddition to the analog photo-resist process. Additionally, there may becertain limitations to the nature of surfaces and associated statisticsthat may be realized when employing the analog photo-resist process, asin the case of optical recording of speckle patterns. In anotherexample, direct laser-recorded analog photo-resist processes may permitsurfaces to be engineered, with fidelity limited primarily by theresolution of the laser spot and the characterization/repeatability ofthe optical recording transfer function.

Functional Specifications of Initial Continuous Surface and Diffuser

Design rules for achieving optimal performance for continuous surfaces(subject to specific theatre geometry) and as described in U.S. Pat.App. Pub. No. 2009/0190210 may be applied to produce the initialsurface. In the case of a polarization-preserving front projectionscreen and also as described in U.S. Pat. App. Pub. No. 2009/0190210,the desired functional specifications are well defined. In principle, solong as the functional specifications are substantially satisfied, thedetailed distribution of surface topography is of no specificimportance. The functional specifications may include, but are notlimited to, PCR, gain profile shape, and visual appearance. Theexception may include designs incorporating azimuth dependence, which islost in the web shuffling process. Some basic characteristics (which maybe the same as the functional specifications) of desired surfaces aredescribed herein.

For naturally occurring diffuser surfaces, for example non-engineeredsurfaces, the characteristics are frequently determined by physicallymeasuring the bi-directional reflectance distribution function (“BRDF”),representing the differential reflectivity per solid angle. Suchmeasurements can also be made with polarization sensitivity, giving aPCR profile. When a BRDF measurement is made over a sampling area thatis large relative to the mean feature size of a scattering unit, theresult may be a relatively smooth profile. Many such surfaces may havethe desirable characteristics of a matte appearance and nearlyLambertian distribution, as the light collected by the eye is the resultof many scattering events from features that are at/below the wavelengthscale. This randomization may be beneficial by creating a uniformappearance (which may include elimination of optical effects due to thespatial coherence of the source at the screen), but may inefficientlyuse light, and may have a negative impact on polarization preservation.

For the subset of diffuser surfaces that preserve polarization well,there may be a close correspondence between the slope probabilitydensity function and the BRDF. This is because virtually all lightreflected by the diffuser is the result of single scattering events. Aviewer receives light from appropriately oriented contours of thesurface which represent mirror-like specular reflections. To the extentthat the angles are reasonably small (so that the differences betweencomplex S and P reflections can be neglected), such interactionscompletely preserve the state of polarization locally. Also, selectionof feature size and distribution may be important to avoid the grainyappearance (particularly at large observation angles) associated withlow spatial density of appropriately sloped surface. This may also be animportant consideration in the specular direction, where superpositionof partially coherent light can cause speckle. One aspect of the presentdisclosure seeks to utilize web shuffling to capitalize on the surfacecontrol available in processes, such as UV embossing, UV casting,thermal embossing and so on, for creating optimized surfaces. UVembossing may be desirable method to reproduce fidelity.

Fabrication of Discrete Surface Elements

According to one aspect of the present disclosure and returning to FIG.3, the diffuser 320 may be diffuser roll-stock and may be fabricatedusing various processes such as, but not limited to roll-to-roll UVembossing, UV casting, thermal embossing and so on. The embossingprocess may be followed by vacuum deposition of optical coatings orlayers. As depicted in FIG. 3, the optical coatings or layers mayinclude a release coating 330. In an exemplary embodiment, fourthin-film layers may be included such as the release coating 330,optical layers 340 and reflective layer 350. One purpose of the releasecoating 330 may be to facilitate the stripping of the optical layers 340and reflective layer 350 in a subsequent step, in a manner that mayleave substantially no residue or surface roughness, as described inU.S. Pat. No. 5,672,410, which is hereby incorporated by reference. Theoptical layers 340 may form a sandwich structure, and may be transparentdielectric films bounding a reflective layer 350. The reflective layer350 may be a highly reflective metal layer. In one embodiment, theoptical layers 340 may be dielectric layers and the reflective layer 350may be an aluminum layer. The dielectric layers may serve to passivatethe aluminum and may preserve the mechanical integrity of the structurein subsequent process steps, as described in, for example, U.S. Pat. No.6,383,638, which is hereby incorporated by reference. In the absence ofthe mechanically balanced sandwich structure, released particles maycurl and wrinkle, thus distorting the particle slope probability densityfunction. Moreover, the sandwich structure may be better able towithstand the violent process of stripping, sizing, coating, and drying,without deformation and further reductions in particle size statistics,which may have negative impacts to screen performance.

In one embodiment, optical layers 340 may be dielectric layers (e.g.,SiO₂, SiO, SiO_(x), MgF₂ and so on) and may have an important functionin the formation of particles. Although ductile fracturing of rawaluminum may result in changes to particle slope statistics, thedielectric layers may facilitate brittle fracture, due to the dielectricproperty of high compressive strength relative to tensile strength. Thefirst dielectric support layer which may be adjacent to the diffuser,may be coated in such a way that it will crack along random contours ofthe diffuser structure, which in the absence of further measures, mayultimately produce a broad spectrum of particle sizes. In one example,the initial dielectric support layer may be formed via deposition in adirection normal to the substrate 310, such that the initial dielectricsupport layer may be relatively thin in highly sloped regions. It istherefore possible that the initial dielectric support layer may berelatively weak, and thus, may crack where slopes are highest.

The initial stripping process may involve, for example, immersing thefilm in an ultrasonic bath containing a solvent. Typically, this mayproduce particles that are too large for a spraying process and theparticles may be subsequently sized down. Examples of sizing processesmay include, but are not limited to, grinding, jet milling, or any highspeed collision of the particles with a hard surface (or each other)that can be used to break the particles further. Depending upon a numberof process parameters, the mean particle size may be selected, eventhough the spread in the particle size spectrum may be typically quitebroad. Without further processing and selection of the mean particlesize, the spread in the particle size spectrum can limit the potentialperformance of the resulting screen. In one example, using conventionalspray-painting processes, extremely large particles may need to beeliminated in order to avoid clogging the gun. A clogged gun reducesmanufacturing throughput, and may limit the quality of the product dueto spatter and large macroscopic clumps that may degrade the cosmeticquality of the screen. Additionally, small particles can uniformlydestroy both the desired scatter profile and the PCR through mechanismsdiscussed subsequently.

The formation of discrete diffuser particles via stripping may representa second statistical process. The stripping process may affect theresulting screen behavior largely through the statistics of particlesize, and in particular, the size of the diffuser particles relative toother significant features. The stripping process may also liberate theoptically functional layers from the supporting diffuser sheet, thuserasing memory of the particle orientation (including sign of surfacenormal vector) with respect to the substrate. Thus, while the strippingand coating process steps may be statistically coupled, the generalcontribution of particle orientation may be primarily attributed to thecoating process step.

FIG. 4 is a schematic diagram illustrating a spectrum 400 of featuresizes and the ranges associated with particular screen. Diffuser featuresize 410 may be configured to be significantly larger than a wavelengthof illuminating radiation in order to assure that polarization can belocally preserved in reflection as indicated by the local statisticsrange 420. Above this limit (this limit may refer to the length scaleapproximately one micron above which reflection happens specularly andbelow which light is scattered; e.g., not determined by Frensel, butinstead determined by diffraction), interactions of light with thesurface are described by specular reflections in the long rangestatistics 440, with behavior appropriately predicted by Fresnel'sequations. When probing a surface at the long-range statistics 440 scale(and moderately above), statistical scatter profiles are sparselydistributed (converging to the deterministic at the extreme low-end) asthey represent localized events. As the probe area increases, thescatter statistics become more complete and thus begin to describe thecharacter of the macroscopic surface.

The spectrum 400 assumes a surface containing a random distribution ofdiffuser feature sizes, where a deterministic structure (e.g., a lensletarray) would have a much narrower distribution. Spectrum 400 also showsone possible typical distribution of a particle size range 430, whichmay vary significantly with the diffuser feature size 410 distribution.In one embodiment, minimal overlap of these distributions may bepreferred, and in the optimized case, the distributions may besignificantly separated. The overlap region 450 represents the rangeover which diffuser feature size and particle size may be comparable,and in some instances, a particle may comprise only a portion of asingle diffuser feature.

According to an exemplary embodiment, the particle size may besignificantly larger than the largest diffuser feature size, and assuch, the statistics may become more complete. Such particles maycomprise the vast majority of the pigment used to coat the screen. Thesmallest scale at which a robust representation of the macroscopicsurface is attained may be associated with long-range statistics 440.Within the long-range statistics 440, the scatter profile may be smoothand may be virtually indistinguishable from that measured by probingsignificantly larger areas. For a surface having random sized diffuserfeatures, the scale at which long-range statistics are captured may besignificantly larger than the largest particle size. While thissituation may be less than ideal, it is common when considering thepractical limitations of pigment size. If the surface is deterministic,it may be feasible to capture long-range statistics at a much smallerscale. Regardless, the gap between particle size and long-rangestatistics may be preferably minimized.

At still larger scales, such as the range of ensemble statistics 460,the screen viewing conditions may be such that any non-uniformity in thescreen is visually resolvable, and would therefore be objectionable.Such non-uniformities, also referred to as screen structure, typicallymay be observed as a random noise image, or fixed-pattern noise, whichcan detract from the quality of both 2D and 3D presentations. Screenstructure may manifest itself as a subtle modulation in the observedintensity, as well as a localized loss in PCR, depending upon thespectrum of feature sizes associated with the artifact. At this scaleand larger, there may exist visually resolvable coating defects, drift,and distortions to the scatter profile, due to lack of process controlin manufacturing both the tooling and the base material. Moreover, thediffuser can have directionality, which can also drift spatially. Notethat the nature of this defect may be a low-contrast macroscopicdisruption in the gain, versus a point defect, for instance, a defectassociated with hot-spotting. As will be discussed herein,relatively-small point defects of very high contrast may produce sharpchanges in gain that are also unacceptable.

The ensemble statistics 460 may represent substantially all possibleoutcomes, which in this context, may be measured at the scale of thefinished screen. Ensemble statistics 460 may be associated with both theraw diffuser used to create the pigment (prior to stripping), and thefinal coated screen. The degree to which raw diffuser and finishedscreen ensemble statistics resemble each other may be highly dependenton relative feature size, as will be discussed in detail below.

According to an exemplary embodiment, a particle may be large enough tocapture long-range statistics subject to the limitations of theuniformity of the embossing process, but the particle may be smallerthan any visually resolvable defect requiring homogenization. Given thelimitations on the upper limit of pigment size, the former may bedifficult to satisfy, while the latter may be straightforward in acinema environment. Additionally, web shuffling may further be useful inhomogenizing smaller defect features that, while not visuallyresolvable, may represent large disruptions in the intensity. Forinstance, voids may be produced in various process steps such as, butnot limited to, UV embossing or tool manufacturing due to bubbles, whichwhen metalized, produce highly reflective facets in the plane of thesubstrate. While such defects may be small (on the order of a fewhundred microns, for example), nearly all of the incident radiation isre-directed along the specular direction. The result is an abrupt spikein intensity (or sparkle) that upsets the homogeneity of the image, andthus degrades the appearance. Such facets are on a relatively dimbackground diffuser, which redirects incident light into a broad solidangle, in accordance with the BRDF.

FIGS. 5A and 5B are schematic diagrams respectively illustrating oneembodiment of a defect before and after web shuffling. For instance,FIG. 5A shows defects on substrate 500 before web shuffling, and FIG. 5Bshows defects on substrate 510 after web shuffling (not illustrated toscale). On substrate 500 (before web shuffling), defects or individualfacets 520, 530 may be several hundred microns in diameter, and as such,can potentially be homogenized by web shuffling. Individual facet 520includes fracture lines 520 a, 520 b, 520 c to produce flake particles521, 522, 523 and 524. Likewise, individual facet 530 includes fracturelines 530 a and 530 b to create flake particles 531, 532 and 533.Although the material surrounding individual facets 520 and 530 may alsobe fractured, for purposes of discussion, only the fracture lines in theindividual facets are illustrated in FIG. 5A. After web shuffling,substrate 510 includes flake particles 521, 522, 523, 524, 531, 532 and533 randomly distributed on the substrate 510.

While defects as illustrated in FIG. 5A may not be completely eliminatedat the particle scale, reducing the area of facets can mitigate theimpact on visual quality. At a larger scale, clusters of such defects,and clusters that repeat due to flaws in tool manufacturing, may belikewise homogenized. Clusters of small specular facets are oftenassociated with the hot-spot effect, which may manifest as a spike inthe gain profile along the specular direction. Release of the particlesfrom the substrate and re-coating may provide sufficient tiltrandomization to substantially eliminate this effect.

In another exemplary embodiment, scatter profiles measured on the scaleof a visually just-resolvable-area (“JRA”) of the finished screenmaterial may virtually capture the ensemble statistics of the rawdiffuser. A goal of web shuffling may be to reduce the scale required tocapture ensemble statistics by averaging material in azimuth andposition at the scale of a JRA. In a cinema environment, the averagescale may be on the order of 1 cm or larger for low-contrast structure.

According to another exemplary embodiment, differences betweenlong-range statistics and ensemble statistics may be substantially heldto a predetermined tolerance in the manufacturing of the base diffusermaterial. To reduce or avoid unnecessary texture in the appearance ofthe finished screen, it may be preferred that the observed intensitystep between any two adjacent particles of the ensemble (with anyrelative azimuth orientation) is below a just-noticeable-difference(“JND”). At the extreme of (large) visually resolvable particles, thismay be approximately one percent of the mean intensity. In one example,a particle may be much smaller than a JRA, which may tend to loosen thetarget uniformity. Moreover, even if such steps greatly exceed a JND, itmay be tolerable provided that the texture is subtle, and again, theparticles are small with respect to a JRA. Such is the case for typicalpigment size distributions, observed in a cinema environment.

A useful performance metric may be the ratio of particle area to meandiffuser feature area, or particle-to-feature-ratio (“PFR”). The PFR isa direct measure of the ability of a particle to capture long-rangediffuser statistics. The PFR may also be an indirect measure of theparticle aspect ratio (ratio of average particle in-plane dimension topeak-to-valley thickness) and the probability of a particle preservingorientation when transferred from carrier substrate to screen substrate.Specifically, the original diffuser typically satisfies the desiredscatter requirements using surface peak-to-valley heights that are small(roughly 20%) relative to in-plane dimensions. A particle with a largePFR thus has a large aspect ratio. Such particles have the appearance ofbumpy wafers, which tend to stack so as to best preserve the originalslope probability density function in the coating process. Thus ingeneral, a large PFR may be preferred in order to ultimately realize thebenefits of a structured particle.

For random surfaces, each particle samples the ensemble, and thus eachparticle may provide a unique and incomplete representation of thesurface statistics. Statistics are more complete when the PFR is larger,and therefore a particle comes closer to faithfully representing theoriginal surface. This argues for the largest possible particles(provided that the particles are not distorted/broken during subsequentprocessing, and provided the particles are still small with respect to aJRA), with the smallest diffuser features possible. In conventionalspray-painting processes, there are limitations to maximum particle sizebefore coating difficulties can arise. Extremely large particles areeliminated or they clog guns, producing macroscopic artifacts anddecreasing manufacturing throughput. In conventional painting processes,an approximate size range may be up to 200 microns with 50 microns morepreferable. In one embodiment, painting processes may include particlessizes exceeding 300 microns.

Additionally, the minimum feature size possible may depend upon theoptical recording process. In an image recording process (e.g.,speckle), there may be challenges to resolving very small speckles dueto the quality of the imaging system and opto-mechanical stabilityissues. Vibrations that occur during recording may tend to impact thequality of the master due to blur. However, it is reasonable to expectthat mean feature sizes of approximately five microns may be possiblewith either image (e.g., speckle) recording or direct laser writtenengineered surfaces. A PFR of roughly 100 should be adequate to capturemost of the statistics of a randomized surface. But there remains anissue that the particle size spectrum is quite broad with fracturing ofrandom surfaces, resulting in a significant number of particles (fines)that are on the order of a feature size, or even smaller.

In the case of recording arbitrarily small features, the lower limit maybe approximately one micron, which may ensure that polarization ispreserved on reflection. It may be difficult, however, to employ thelower limit with the coating of discrete particles due to the influenceof hard edges. A crossed-polarizer microscope measurement allows one tovisualize the PCR directly on the surface to identify the source ofcrossed polarizer leakage. In a crossed-polarizer microscopearrangement, individual particles appear brightly outlined, as if theimage of the diffuser surface were high-pass spatial filtered. Thescatter from edges is generally “white” in angle space, such that thiscontribution to the resulting PCR tends to follow the gain profile Metalflake pigments typically contain a significant population of low PFRparticles, which may contribute significantly to the density of suchedges, thus causing significant loss in PCR. With an optimized coatingprocess, PCR tends to grow with particle size due to the associatedreduction in the area density of edges.

There are two primary benefits to controlling the particle sizedistribution in manufacturing. The first is improvement in particlestatistics that impact the screen performance, and the second isimprovement in pigment yield, which drives cost. According to oneembodiment of the present disclosure, the master recording process canfurther contain a technique for controlling the subsequent particle sizedistribution. This can be done with the addition/superposition offeatures that control the breakage of material when stripped from thesubstrate. Such “control-joints,” which can take the form of a grid, mayprovide a much tighter distribution in the particle size statistics. Tothe extent that control joints do not typically introduce artifacts,such as perimeter facets, such an approach may provide a better screenperformance and pigment yield. Alternatively, a particle-spectrumlow-pass filtering operation may be employed to strip the pigment of thesmall particles that harm performance.

In the event that the particle sizes are sufficiently small such thatweb shuffling may randomize the diffraction artifacts (e.g., withspray-painting processes), it may be possible to use the teachingsherein with deterministic microstructures such as, but not limited to,periodic structures. As used herein, deterministic may be understood asreasonably and/or statistically predictable, specifically designed or asunderstood by one of ordinary skill in the art. Periodic structures canhave uniform peak-to-valley feature heights, improving the probabilitythat particles may retain a desired orientation. Furthermore, periodicstructures can have built-in control-joints, which may substantiallyeliminate the need for additional process steps in the recordingprocess. This may introduce break-points that are substantiallyregistered with respect to the diffuser features. Deterministicmicrostructures can be designed to capture long-range statistics with arelatively low PFR. Further, even a single diffuser feature may providea full representation of the desired scatter profile.

Coating of Discrete Surface Elements

A coating process of the present disclosure may provide a surface thatclosely approximates that of the initial continuous diffuser.Additionally, when using the averaging benefits of web shuffling, thesurface produced may be similar to the initial continuous diffuser. Inprinciple, this may be accomplished by using a relatively small numberof large particles, in which the large particles may contain an adequaterepresentation of the long-range statistics, and may be tiled on thesurface with minimal overlap. The tiling with minimal overlap maysubstantially minimize shifts in the slope statistics due to tipping ofparticles, while providing high fill-factor (ratio of reflective area tototal area), with substantially minimal waste of pigment. Such a surfacealso may have substantially minimal edge density, thus substantiallymaximizing PCR. While processes exist for coating very large particles,this scenario may not be practical for many conventional coatingprocesses. In one embodiment, it may be preferred to provide a particlesize range of approximately 100 microns or smaller.

Typically, the coating process may involve mixing the reflectiveparticles into a fluid, such as the fluid 230 discussed with respect toFIG. 2. The mixture can be coated onto the substrate using any number ofmethods known in the art, with spray-painting being the most common.Spray painting may be more effective than printing methods for coatingpigments with larger dimensions.

In conventional projection screen manufacturing, strips of a plasticizedsubstrate, typically having a width between one and two meters, arewelded together, hung, and stretched onto a frame. Spray rigs thenraster the position of the gun until adequate coverage is achieved. Theoptical properties of the coated surface depend upon several statisticalvariables, which among other things include the geometricalcharacteristics of the particles, the volume ratio of pigment to binder(“PBR”), dilution, any additional additives such as matting agents, orflame retardants, and the detailed coating methodology. In oneembodiment of the present disclosure, the coating requirements areunique, in that statistics may be determined by intra-pigmenttopography, and in which coating may be a deterministic process. Thatis, the coating process may substantially minimize the role of particletipping statistics on the scatter profile. An exemplary embodiment ofthe coating process may produce a virtually continuous metal surface atthe optical interface, with substantially minimal resin overcoat (toprovide mechanical integrity and durability). The optical interface maybe the optically functional layer of pigment or the layer that mayredirect projector light to the audience, which is ideally as planar aspossible. This may be achieved in wet coating using leafing metalpigments, which may float to the surface and may self-assemble into adense planar optical interface. The dense optical interface may exist ineither one of or both, in-plane (maximizing fill-factor), and in thethickness direction. Leafing pigments have a high surface tension, andthus, may not be wetted by the binder matrix and may rise to thesurface. In the manufacturing of ball milled aluminum, agents such asstearic acid are often used, which typically modifies the surfacetension and increases leafing. The leafing process produces high fillfactor with minimal pigment, due to the tendency for particles to flowand fill gaps at the top surface. The mobility/diffusion-rate during thedrying process depends upon particle size/weight.

In the limit of a large PFR, diffuser features represent surfaceperturbations, and as such, there is a well defined global surfacenormal. Any deviation of this particle surface normal from the screensubstrate normal may be considered the particle tip angle, and mayprovide an associated slope probability density function for the coatedsurface. Given the random nature of coating, this is an azimuthallysymmetric function that tapers smoothly from a peak in the substratenormal direction (e.g., Gaussian). According to the present disclosure,the coating process may substantially minimize the width of the particleslope probability density function, and may produce a dense stack ofparticles lying nominally in-plane at the surface. A particle slopeprobability density function of significant width may broaden theoverall screen slope probability density function. Additionally, unlike(mirror-like) flat, bright, metal flake pigments which may havethickness determined primarily by the optical coating stack, the surfacetopography of pigment of the present disclosure may be an importantaspect of the potential density achievable in the thickness direction.High density in the thickness direction at the surface may achieve oneor more of the following—minimizing particle tipping, minimizing theoptical contribution of the binder, and minimizing additional surfacedepth, which can trap light, produce shadowing, light loss, and multiplescatter events. Again, it may be preferable to obtain the desiredstatistics with minimal feature size, so that the effective thickness ofa particle is substantially minimized.

While particle tipping may broaden the distribution of the particleslope probability density function, another mechanism, particle slump,may narrow the distribution of the particle slope probability densityfunction. There may be a lack of separation or overlap between thediffuser feature size spectrum and that of the particle size spectrum(shown as the overlap region 450 in FIG. 4), and this may cause asignificant difference between the raw diffuser ensemble statistics andthe ensemble statistics of the finished screen. Each particle may have amean surface normal vector (“MSNV”) prior to stripping. The particlestatistics may be preserved by preserving this angle throughout thestripping and coating processes. As a particle becomes comparable to, orsmaller than, a diffuser feature, the statistics begin to take onlocalized characteristics. When this occurs, the probability density forthe MSNV may begin to broaden, and may become the ensemble slopeprobability density in the small particle limit. In the large particlelimit, the MSNV probability density may converge to that of thesubstrate normal. Between these limits, the diffuser characteristics maybe substantially preserved in the web shuffling process, provided thatthe information contained in the MSNV spectrum is likewise preserved.With that said, the particles may “slump” when stripped from the carriersubstrate and make it difficult to preserve the information contained inthe MSNV spectrum.

When the MSNV spectrum is broad, it may be an indication thatsignificant slope information may be lost in the stripping andsubsequent coating process. By example, if the diffuser structure wereremoved from beneath each particle, the particles could tend to fall, orslump, onto the underlying substrate. The result could be a general lossin slope, and an associated narrowing of the gain profile. Following inthe coating process, small particles that carried little information oftheir original slope could be conformal to the slope of largerunderlying particles, which helps the situation. Of note, the behaviorof leafing pigments in binder is not adequately described by thisexample. Nevertheless, the general tendency is again for a loss in gainwidth due to the slump phenomenon. A desirable way to address this issuemay be to maintain high PFR for most or all of the particles of theensemble. In an embodiment, the mean diffuser feature size may be in theapproximate range of five to ten microns, the mean particle dimensionmay be in the approximate range of 70-90 microns, and minimal particlecount below approximately twenty microns.

Web shuffling may be associated with spatial redistribution ofparticles, inversion of (statistically) 50% of the particles, andrandomization of particle azimuth. In practice, web shuffling may alsobe accompanied by the impact of particle slope probability distribution,slump, and edge effects. The significance of the latter may dependmostly on the relative size distribution of particles to diffuserfeatures, or PFR. When PFR is universally high, the visual appearance ofa screen may be substantially determined by the scale of the diffuserfeatures, rather than at the scale of the particle. This can becontrasted with a screen composed of flat metal leafing pigments, wherethe scale of the particle is the most important feature. Alternatively,the desired method for substantially homogenizing the appearance of ascreen that requires primarily single reflection events to preservepolarization, may be to reduce the scale of the scattering features.Given that the particles of the present disclosure may include diffuserfeatures that are approximately a few microns, the appearance may bemore likely to resemble that of a conventional 2D matte screen. Incontrast, a screen composed of a flat metal leafing pigment that is tensof microns in mean size is more likely to have a coarse granularappearance.

Web shuffling may be an effective technique for substantiallyhomogenizing the appearance of a screen at the scale of a JRA andlarger. However, at this scale and smaller, one aspect of the visualquality of a screen may concern the texture of a screen. One example ofthe present screen may be considered a surface that randomly(discretely) samples the projected image in reflection. From aparticular viewing position relative to the screen, the vision systemforms an image of this object on the retina.

In another example, the screen may be composed of a random distributionof small planar mirror facets. Depending upon random tip/tilt, eachfacet may steer an incident plane wave along an observation direction.If spatial sampling is sparse, then the image may appear grainy, but ifthe mean path between apertures is much smaller than a JRA, then theimage may appear relatively smooth. In a conventional screen using flatmetal leafing pigments, the mean image sampling scale is associated withthe pigment size, with the mean path between samples being substantiallylarger (dependent upon the slope probability density function).Alternatively, the pigments of the present disclosure may providesampling at a much smaller scale (for example, at that of the diffuserfeature size). In one example of the present disclosure, a 50 micronparticle may contain five micron diffuser features, and the number ofsamples may be 100 times that of an identical sized flat metal pigment.While these pigments may be discrete particles, the behavior may notdefined by the particle perimeter (to first order), as with flat metalpigments. Additionally, second order effects may be associated withparticle slope probability and particle edges. Further, theintra-particle structure may provide a robustness against particletipping, and the contribution of edges may be somewhat decoupled.

Thus, it may be preferred that diffuser features are very small relativeto the scale at which the eye can resolve structure. The scale may beeither a just-resolvable-dimension (“JRD”) or JRA. The latter may ensurethat the perception of surface uniformity is the result of (incoherent)superposition on the retina over contributions from many reflectionevents. According to an exemplary embodiment, there may be a largenumber of such contributions from individual particles along anyobservation direction, thus creating a matte appearance.

The ability to discern screen texture may be limited by the angularresolving power of the vision system optics, and the sensor (retina)resolution. Normal vision may correspond to recognizing letters thatsubtend an angular height of five minutes of arc, with each element ofthe letter subtending one minute of arc. Such tests are done using mediawith sharp edges, black on white, in a high ambient environment.Furthermore, this test may be primarily for that part of the eyecorresponding to the fovea of the retina. Outside of the zone of highestresolution, the visual acuity may fall by 50% in approximatelytwo-degrees. Moreover, visual acuity may fall in reduced ambientlighting environments. The current cinema brightness standard is 14 flfor 2D presentation, and as low as 4.5 fl for 3D presentation, so visualacuity may significantly degrade due to increased aberrations as thepupil dilates. Finally, visual acuity may be a function of contrast.Subtle random modulation in intensity may be more difficult to resolvethan periodic black/white bars. Since the peak sensitivity of the eye isat a low spatial frequency of two to three cycles/degree, ajust-resolvable spatial frequency (associated with a JRA) shifts long asthe modulation depth is decreased. At approximately 100% sinusoidalmodulation, it may be possible to resolve approximately 7 mm at about 12meters distance, but at approximately 10% modulation, the resolution maydegrade to approximately 13 mm, and at approximately 2% modulation, theresolution may degrade to approximately 50 mm. Given the nature ofrandom screen non-uniformities, it is thus reasonable to assume that aJRA of screen surface may be between approximately one and fivecentimeters at a typical cinema viewing distance. At dimensions smallerthan a JRA, there may be a spatial averaging that occurs, associatedwith the sensitivity weighted modulation transfer function (MTF) of thevision system.

In another exemplary embodiment, web shuffling may be leveragedspecifically to produce a desired scatter profile via azimuth averaging.An asymmetric scatter profile, when azimuth averaged, can be used toshape the scatter profile on the scale of a JRA. However, the azimuthdependence can be pronounced and thus affect a significant influence onthe uniformity of the scatter profile, a larger ratio of JRA to particlesize may be required to avoid texture issues. An analogous situation mayexist when there is significant spatial variation in the scatter profileof the source substrate, or when two types of particles are mixed toproduce desired spatial-averaged scatter profiles. In one exemplaryembodiment, two distinct types of particles may be manufactured, withmultiple products being defined by the mixing ratio. For instance, amid-range profile can be produced by the appropriate mixture ofhigh-gain and low-gain particles.

FIG. 6 is a flowchart illustrating operations of one embodiment of amethod 600 for providing a projection screen. Although the flowchartincludes operations in a specific order, it may be possible to performthe operations in a different order, and it also may be possible to omitoperations as necessary. The flow chart may begin with the operation ofblock 610, in which an optically smooth surface may be provided. Aspreviously discussed, the optically smooth surface may be provided usinga manufacturing tool with a predetermined topography. Next, in theoperation of block 620, the diffuser may be fabricated using theoptically smooth surface. The diffuser may be diffuser roll-stock andmay be fabricated using any number of processes such as roll-to-roll UVembossing.

In the operation of block 630, at least a first optical coating may bedeposited on the diffuser. The first optical coating may be a releasecoating. A second optical coating may also be deposited subsequent tothe first optical coating or may also be deposited adjacent to thediffuser in the absence of the first optical coating. The releasecoating may facilitate a subsequent stripping processed describedherein, between the second optical coating and the diffuser. The secondoptical coating may be a dielectric material such as, but not limitedto, SiOx, MgF₂, and so on. Additionally, as discussed with respect toFIG. 3, the dielectric may be deposited in such a way as to crack alongrandom contours of the diffuser structure. Alternatively, in oneembodiment and as previously discussed, the dielectric material maycrack along “control-joints,” which may take the form of grid-likefeatures introduced into the diffuser structure.

In the operation of block 640, a reflective layer may be deposited onthe second coating. The reflective layer may be a metal layer such asaluminum, but may be any type of highly reflective coating. Next, in theoperation of block 650, an additional optical coating may be depositedon the reflective layer. The additional optical may be a dielectriclayer such as, but not limited to, SiOx, MgF₂, and so on. The secondoptical coating and the additional optical coating may form a sandwichstructure. For example, the two optical coatings may be coated on bothsides of the reflective layer.

In the operation of block 660, engineered particles may be created bystripping an optically functional material comprised of the secondoptical coating, the reflective layer and the additional opticalcoating. Stripping the optically function material may be achieved byany number of processes such as, but not limited to, immersing the filmin a solvent ultrasonic bath. The engineered particles that may becreated in the stripping process may be too large to use in the coatingprocess and this may be verified in the operation of block 670. In theoperation of block 670, the engineered particles may be evaluated toverify whether the size falls within a predetermined size range. In theevent the engineered particles are too large, the engineered particlesmay be resized, as shown in the operation of block 680, and thenre-evaluated again as described with respect to the operation of block670. In the event the engineered particles do fall within thepredetermined size range, in the operation of block 690, the engineeredparticles may be combined with a fluid. As discussed with respect toFIG. 2, the fluid may include a transparent binder resin such as, butnot limited to PVC resin, enamel, polyurethane, acrylic, lacquer, andthe like, and/or some form of dilution. The fluid may function as acarrier for the engineered particles. Next, in the operation of block695, the fluid and the engineered particles may be transferred to asubstrate in a coating process. The coating process may include spraypainting or any spray and/or printing method known in the art.

As may be used herein, the terms “substantially,” “substantiallyapproximate(s),” “substantially minimize(s),” and “approximately”provide an industry-accepted tolerance for its corresponding term and/orrelativity between items. Such an industry-accepted tolerance rangesfrom less than one percent to ten percent and corresponds to, but is notlimited to, component values, angles, et cetera. Such relativity betweenitems ranges between less than one percent to ten percent.

While various embodiments in accordance with the principles disclosedherein have been described above, it should be understood that they havebeen presented by way of example only, and not limitation. Thus, thebreadth and scope of this disclosure should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with any claims and their equivalents issuing from thisdisclosure. Furthermore, the above advantages and features are providedin described embodiments, but shall not limit the application of suchissued claims to processes and structures accomplishing any or all ofthe above advantages.

Additionally, the section headings herein are provided for consistencywith the suggestions under 37 CFR 1.77 or otherwise to provideorganizational cues. These headings shall not limit or characterize theinvention(s) set out in any claims that may issue from this disclosure.Specifically and by way of example, although the headings refer to a“Technical Field,” the claims should not be limited by the languagechosen under this heading to describe the so-called field. Further, adescription of a technology in the “Background” is not to be construedas an admission that certain technology is prior art to any invention(s)in this disclosure. Neither is the “Summary” to be considered as acharacterization of the invention(s) set forth in issued claims.Furthermore, any reference in this disclosure to “invention” in thesingular should not be used to argue that there is only a single pointof novelty in this disclosure. Multiple inventions may be set forthaccording to the limitations of the multiple claims issuing from thisdisclosure, and such claims accordingly define the invention(s), andtheir equivalents, that are protected thereby. In all instances, thescope of such claims shall be considered on their own merits in light ofthis disclosure, but should not be constrained by the headings set forthherein.

1. A web shuffling method for providing a projection screen, the methodcomprising: stripping optically functional material from a carriersubstrate, wherein the stripping breaks the optically functionalmaterial into individual engineered particles; and distributing acoating onto a second substrate to achieve a substantially homogeneousoptical appearance of the projection screen, wherein the coatingincludes the individual engineered particles.
 2. The method of claim 1,further comprising fabricating a base diffuser material, wherein thebase diffuser material is adjacent to the optically functional material.3. The method of claim 2, wherein fabricating the base diffuser materialfurther comprises holding a predetermined tolerance, further wherein thepredetermined tolerance is based on at least a difference betweenlong-range statistics and ensemble statistics.
 4. The method of claim 2,wherein distributing the coating provides a surface that substantiallyapproximates that of the base diffuser material.
 5. The method of claim1, wherein distributing the coating is operable to substantiallyminimize the role of particle tipping statistics on the scatter profileof the coating.
 6. The method of claim 1, wherein distributing thecoating further comprises producing a dense stack of the individualengineered particles lying substantially in-plane at the surface of thecoating.
 7. The method of claim 1, further comprising maintaining a highparticle-to-feature ratio for the individual engineered particles.
 8. Aprojection screen with a substantially homogeneous appearance, whereinthe substantially homogeneous appearance is achieved through webshuffling, the projection screen comprising: a substrate; and a coatingadjacent to the substrate, the coating comprising engineered particlescreated by stripping an optically functional material from a carriersubstrate, wherein the engineered particles are operable to primarilydetermine the scattering behavior of light.
 9. The projection screen ofclaim 8, wherein the carrier substrate is a sacrificial carriersubstrate.
 10. The projection screen of claim 8, wherein the morphologyof the engineered particles may be operable to primarily, statisticallydetermine the macroscopic scatter behavior of the projection screen. 11.The projection screen of claim 8, wherein the coating further comprisesa surface operable to decouple the scatter profile from the polarizationcontrast ratio of the projection screen.
 12. The projection screen ofclaim 8, wherein the optically functional material is produced using adiffuser.
 13. The projection screen of claim 12, wherein the diffuser isadjacent to the carrier substrate.
 14. The projection screen of claim12, wherein the optically functional material further comprises at leasta first optical coating.
 15. The projection screen of claim 14, whereinthe first optical coating is adjacent to the diffuser prior to strippingthe optically functional material from the carrier substrate.
 16. Theprojection screen of claim 8, wherein the optically functional materialfurther comprises at least a second optical coating.
 17. The projectionscreen of claim 16, wherein the second optical coating is a dielectriccoating.
 18. The projection screen of claim 16, wherein the secondoptical coating is adjacent to the diffuser prior to stripping theoptically functional material from the carrier substrate.
 19. Theprojection screen of claim 14, wherein the first optical coating is arelease layer.
 20. The projection screen of claim 8, further comprisinga reflective layer.
 21. The projection screen of claim 20, wherein thereflective layer is substantially composed of aluminum.
 22. Theprojection screen of claim 20, wherein the optically functional materialfurther comprises a third optical coating adjacent to the reflectivelayer.
 23. The projection screen of claim 22, wherein the third opticalcoating is a dielectric coating.
 24. The projection screen of claim 8,wherein the engineered particles further comprise a sandwich structure,wherein the sandwich structure includes a plurality of optical coatingson at least a first side of a reflective layer.
 25. The projectionscreen of claim 8, wherein the engineered particles are within apredetermined size range.
 26. The projection screen of claim 25, whereinthe engineered particles are resized if the engineered particles areoutside the predetermined size range.
 27. The projection screen of claim8, further comprising a fluid, wherein the fluid is combined with theengineered particles.
 28. The projection screen of claim 27, wherein thefluid combined with the engineered particles is deposited onto asubstrate.
 29. A method for providing a projection screen, the methodcomprising: stripping an optically functional material from a firstcarrier substrate; creating engineered particles from the opticallyfunctional material; and depositing the engineered particles on a secondsubstrate to create a substantially homogeneous optical appearance ofthe projection screen.
 30. The method of claim 29, further comprisingutilizing a diffuser to provide the optically functional material,wherein the diffuser is adjacent to the first carrier substrate.
 31. Themethod of claim 29, further comprising depositing at least a firstoptical coating, wherein the first optical coating is adjacent to thediffuser.
 32. The method of claim 31, further comprising depositing asecond optical coating.
 33. The method of claim 32, wherein the secondoptical coating is a dielectric coating.
 34. The method of claim 32,wherein the first optical coating is a release layer.
 35. The method ofclaim 29, further comprising depositing a reflective layer.
 36. Themethod of claim 35, wherein the reflective layer is substantiallycomposed of aluminum.
 37. The method of claim 35, further comprisingdepositing a third optical coating adjacent to the reflective layer. 38.The method of claim 36, wherein the third optical coating is adielectric coating.
 39. The method of claim 29, further comprisingcreating the optically functional material by forming a sandwichstructure, wherein the sandwich structure includes optical coatings onat least a first side of a reflective layer.
 40. The method of claim 29,further comprising verifying the engineered particles are approximatelywithin a predetermined size range.
 41. The method of claim 40, whereinverifying the engineered particles further comprises resizing theengineered particles when the engineered particles are not approximatelywithin the predetermined size range.
 42. The method of claim 29, furthercomprising combining the engineered particles with a fluid.
 43. Themethod of claim 29, further comprising depositing the fluid with theengineered particles onto a substrate.
 44. A projection systemcomprising: a projection screen with a substantially homogeneousappearance, wherein the substantially homogeneous appearance is achievedthrough web shuffling, the projection screen comprising a substrate anda coating adjacent to the substrate, the coating comprising engineeredparticles created by stripping an optically functional material from acarrier substrate; and a light projection system directing light in thedirection of the projection screen.